A product using a linked clone method (for example, a Linked Clone Technology® by VMware®) is used as a generation method of a virtual machine. For example, PTL 1 (Japanese Unexamined Patent Application Publication No. 2011-248742) describes a technology related to a storage management system using the linked clone method. PTL 1 describes a technology of a storage system for reducing disk capacity by managing a disk image of each virtual machine as a difference from a master image.
When backing up a virtual machine, data access for duplicating a volume on the virtual machine (referred to as a “virtual volume”) occurs. In some cases, data transfer for transferring the volume to a backup destination may be performed.
PTL 2 (Japanese Unexamined Patent Application Publication No. 2015-15047) describes a technology for making a duplicate of backup source data at a backup destination while eliminating overlap. A system described in PTL 2 is configured to check whether or not particular data are already transferred to a backup destination by comparing data already transmitted to the backup destination with data to be transferred from a backup source.